CN103902820A - Equivalence coefficient method of vehicle structure fatigue damage calculation under combined road conditions - Google Patents

Abstract

The invention discloses an equivalence coefficient method of vehicle structure fatigue damage calculation under combined road conditions. The method includes the steps of firstly, testing the stress load of a vehicle structure under selected combined road conditions and compiling a load spectrum; secondly, calculating vehicle damage value under each road condition; thirdly, according to the damage equivalence principle, using one road condition as reference to calculate the equivalence coefficients of vehicle structure damage under other road conditions; fourthly, using the equivalence coefficients to adjust the combined road conditions according to users' needs, and analyzing corresponding vehicle structure damage. The method has the advantages that the method is based on established fatigue load test data, and the equivalence relation of fatigue damage of each road surface can be conveniently and accurately determined during automobile fatigue durability research; mileage recombination can be performed in road tests according to users' application requirements and targets; fatigue damage value of vehicles can be estimated, and comparative analysis of fatigue damage can be performed conveniently.

Description

A kind of equivalent coefficient method that combines vehicle structure fatigue damage calculating under road conditions

Technical field

The present invention relates to vehicle fatigue durability research field, relate in particular to a kind of for representing to combine the method for vehicle structure fatigue damage situation under road conditions effect.

Background technology

Road roughness excitation directly causes vehicle fatigue damage, for determining the impact of true road excitation on vehicle fatigue durability, conventionally under the each enhanced road surface incentive condition in testing field, carry out the research of vehicle fatigue durability, survey the life prediction under loading spectrum.Each main vehicle research and development institution, full-sized car enterprise pay much attention to, have carried out the research work of the tired durable aspect of many vehicles, mainly concentrate on the road simulation under the loading spectrum of testing field, the researchs such as the tired durable road strenuous test of automobile.In the tired durable research of vehicle, road load test has now become important method, has directly important directive function for product initial stage conceptual design, test of product performance, structure optimization checking, product approval etc.And the vehicle product road endurancing test period is longer, test objective is more single, after product improvement optimal design, still need continuous revision test, greatly increase experimentation cost, simultaneously, fatigue endurance test data under each enhanced road surface obtaining, can not need fully effectively to utilize for the different user of vehicle complete vehicle and parts manufacturing enterprise, for this reason, in vehicle fatigue durability analysis and research process, realize fatigue endurance test data are effectively utilized, can save lot of experiments cost, can conveniently meet again different user needs, different improvement designed good and bad comparative analysis, there is very important engineering significance and using value.

Auto vendor carries out the durable actual road test of a large amount of fatigue in conjunction with self product purpose conventionally, test selects comprehensive road condition to carry out conventionally, obtain the data such as stress, acceleration, displacement of vehicle structure, can further determine vehicle structure damage, and carry out life prediction, also can be vehicle structure and carry out indoor bench test excitation spectrum is provided, and then the fatigue durability energy of definite vehicle product.For the potential impact that under combination road conditions, load test data is not deeply damaged vehicle structure for studying loading spectrum, application target is single, the rule that affects for convenience of the different road conditions conditions of comparative analysis on vehicle structure damage and fatigue lifetime, instruct enterprise to carry out fully effectively utilizing of test figure, reduce the experimentation cost in product development process, the present invention proposes a kind of equivalent coefficient method of calculating vehicle structure fatigue damage under combination road conditions condition.

Summary of the invention

The object of the invention is to: a kind of method that vehicle structure fatigue damage is calculated under the effect of combination road conditions is provided, for the comparative analysis of the vehicle structure fatigue damage based on different road conditions provides a kind of convenient, flexible, reliable research means, for the tired durable research of vehicle provides effective ways.

Technical solution of the present invention is: first the method is to determine combination road conditions, carries out vehicle structure load test and compiling load spectrum under this road conditions condition; Next is the damage of the vehicle structure under various road conditions conditions in calculation combination road conditions; Be according to damage equivalent principle again, take a certain road conditions as benchmark, calculate the equivalent coefficient of vehicle structural damage under other road conditions conditions; Be finally to utilize equivalent coefficient, need to adjust combination road conditions according to user, and analyze corresponding vehicle structure damage.

Wherein, the method comprises the following steps: the first step, alternating load the compiling load spectrum of testing vehicle structure under selected combination road conditions; Second step, calculates the vehicle structure impairment value under each road conditions condition; The 3rd step, according to damage equivalent principle, take a certain road conditions as benchmark, calculates the equivalent coefficient of vehicle structural damage under other road conditions conditions; The 4th step, utilizes equivalent coefficient, need to adjust combination road conditions according to user, and analyzes corresponding vehicle structure damage.

Wherein, the concrete steps of the method are as follows:

The first step: alternating load the compiling load spectrum of testing vehicle structure under selected combination road conditions

(1) determine combination road conditions, select three kinds and the above lower strengthening road combination of pavement grade;

(2) structural loads test, carries out load test to the damage dangerous point of vehicle important structure;

(3) compiling load spectrum, application rain flow method carries out respectively counting statistics to vehicle structural loads under each single road conditions effect.

Second step: calculate the vehicle structure impairment value under each road conditions condition

Application glyphworks software programming Fatigue Damage Calculation flow process, according to the S-N characteristic of vehicle structure material, calculates the fatigue damage of vehicle structure under every kind of road conditions effect.

The 3rd step: according to damage equivalent principle, take a certain road conditions as benchmark, calculate the equivalent coefficient of vehicle structural damage under other road conditions conditions

(1) suppose that the fatigue damage producing equates (being Fatigue Damage Equivalence) with the damage producing under i kind road surface under j kind road surface, have the relation of formula (1) to set up,

$\frac{x_j}{y_j}=\frac{x_{\mathrm{ij}}}{y_i}$ Formula (1)

In formula, x _jrepresent j kind road surface mileage, x _ijrepresent equivalent mileage when i kind road surface is equal with respect to j kind pavement damage, y _jrepresent x _jthe fatigue damage amount that mileage effect produces, y _irepresent i kind road surface x _ithe fatigue damage amount that mileage effect produces;

(2) calculate that under arbitrary road conditions condition, vehicle structure fatigue damage is with respect to the equivalent mileage of fatigue damage under a certain concern road conditions condition, through type (1) calculates and tries to achieve:

$x_{\mathrm{ij}}=\frac{y_i{\·x}_j}{y_j}$ Formula (2)

From formula (2), x _iwith x _ijequivalent, i.e. x _ijto i kind road surface mileage x _iequivalent mileage;

(3) calculate under arbitrary road conditions condition vehicle structure fatigue damage with respect to the equivalent coefficient α of fatigue damage under a certain concern road conditions condition _ij, can further try to achieve equivalent coefficient α by formula (2) _ij, i.e. formula (3),

${\mathrm{\α}}_{\mathrm{ij}}=\frac{x_{\mathrm{ij}}}{x_i}$ Formula (3)

The 4th step: utilize equivalent coefficient, need to adjust combination road conditions according to user, and analyze corresponding vehicle structure damage

(1) according to Automobile Enterprises or user's needs, optional test mileage X _i(comprise road conditions kind j and weight proportion m thereof with test combinations road conditions condition _j);

(2) utilize the equivalent coefficient on each road surface of calculating in the 3rd step, determine all kinds of road conditions test miles X _j; X _jcalculate and try to achieve by formula (4),

$X_j=\frac{X_i\·m_j}{{\mathrm{\α}}_{\mathrm{ij}}}$ Formula (4)

(3) the total damage D under computational analysis target road conditions, can be by asking for the fatigue damage D of every kind of road conditions _jtry to achieve, have formula (5)

D=ΣD _j

$D_j=\frac{y_i}{x_j}\·X_j$ Formula (5)

Advantage of the present invention is: the fatigue load test figure based on set, in the time carrying out the research of automobile fatigue durability, can determine easily and accurately the equivalent relation of fatigue damage between each road surface; Can, according to user's request for utilization and target, in actual road test, carry out mileage restructuring, effectively adjust testing program; Can estimate out the fatigue damage value of vehicle structure, be convenient to carry out the comparative analysis of fatigue damage.The damage of the definite vehicle structure of the method has test basis, and process is easy, contrast is accurate, save a large amount of experimentation cost, for the comparative analysis of vehicle structure fatigue damage, fatigue endurance test research etc. provide a kind of science, reliable, practical method.

Accompanying drawing explanation

Fig. 1 is the scheme schematic flow sheet of the inventive method.

Fig. 2 is control arm structural finite element analysis figure of the present invention.

Fig. 3 is control arm load test paster arrangenent diagram of the present invention

Fig. 4 is rain-flow counting result histogram under control arm combination road conditions of the present invention.

Embodiment

Further describe technical solution of the present invention below in conjunction with specific embodiment, embodiment should not be understood as the restriction to technical solution.

Embodiment 1: press Fig. 1 flow process, the Analysis of Fatigue take certain vehicle control arm under testing field strengthening combination road conditions describes as example.

The first step: vehicle control arm is alternating load test and compiling load spectrum under testing field combination strengthening road conditions.

(1) determine combination road conditions, select Ministry of Communications's road test field enhanced road surface (totally 8 kinds of road conditions), as shown in table 1;

Table 1 testing field load test scheme

(2) structural loads test, vehicle control arm structural damage dangerous point is determined in finite element analysis, as shown in Figure 2, carries out load test, control arm structural loads test patch position is as shown in Figure 3;

(3) compiling load spectrum, application rain stream method is carried out respectively counting statistics to eight kinds of road conditions load, and the rain-flow counting result of control arm measuring point load under combination road conditions is as shown in Figure 4.

Second step: calculate respectively vehicle structural damage under each road conditions.

Application ncode8.0glyghworks analysis of fatigue software calculates the fatigue damage value of vehicle structure under every kind of road conditions, and result of calculation is in table 2.

The each enhanced road surface in table 2 testing field causes the fatigue damage of control arm

The 3rd step: according to damage equivalent principle, take ordinary highway as benchmark, calculate the equivalent coefficient of vehicle structural damage under other 7 kinds of road conditions conditions.

(1) suppose that the fatigue damage producing at ordinary highway condition lower control arm equates (being Fatigue Damage Equivalence) with the damage producing under other road surfaces, by respective value substitution formula (1) in table 2, i.e. x _j=x ₈=2300, y _j=y ₈=4.70E-09, y _i=y ₁, y ₂..., y ₇, its value is respectively 7.81E-07,6.22E-07,1.28E-06,1.05E-07,3.62E-07,5.89E-07,4.36E-08;

(2) calculate respectively vehicle control arm structure fatigue damage under road conditions 1～7 condition and, with respect to the equivalent mileage of fatigue damage under ordinary highway condition, calculate and try to achieve by formula (2), the results are shown in Table shown in 3;

The equivalent mileage of 1～7 pair of ordinary highway of table 3 testing field road conditions

(3) calculate the fatigue damage of vehicle control arm structure under road conditions 1～7 condition with respect to the equivalent coefficient of fatigue damage under ordinary highway condition, the mileage substitution formula (3) of 1～7 correspondence of road conditions in result of calculation and table 2 in table 3 is tried to achieve to each α _ijbe worth as shown in table 4.

The equivalent coefficient of 1～7 pair of ordinary highway of table 4 testing field road conditions

The explanation of equivalent coefficient 4496 numerical value in table 4, every 1m distortion road road conditions, to the caused fatigue damage of vehicle control arm structure, are equivalent to the caused fatigue damage value of ordinary highway road conditions of 4496m.

The 4th step: calculate the vehicle structure impairment value under arbitrary combination road conditions condition.

(1) certain Automobile Enterprises is for certain vehicle, investigate the vehicle structure fatigue durability energy of 30000km ordinary highway condition, according to test condition, test intended is selected distortion road, Block Road third, Block Road second, pebble path second, gravel road, washboard road second, long wave road, and its test miles weight coefficient is got respectively 5%, 20%, 15%, 16%, 25%, 6%, 13% (coefficient value can be adjusted according to actual needs);

(2) utilize in table 4 equivalent coefficient on each road surface of calculating, can determine the test miles of all kinds of road conditions according to formula (4), be shown in Table 5;

The each road conditions test miles of table 5

(3) according to each road conditions mileage in table 5 and table 2 and damage result, the total damage that is calculated vehicle control arm structure in the test of target road conditions by formula (5) is 6.13E-5.

In four-step calculation process, ownership goal mileage, Surface of Trial Pavement kind and weight are determined by different Automobile Enterprises, vehicle, test condition, in the time that needs are adjusted, utilize equivalent coefficient, convenient definite test road conditions mileage, the vehicle structure of being convenient to contrast under corresponding conditions damage.

Claims (1)

1. one kind is calculated the equivalent coefficient method of vehicle structure fatigue damage under combination road conditions condition, it is characterized in that utilizing damage equivalent principle, ask for the equivalent coefficient of the vehicle structure damage between each road conditions under combination road conditions condition, and utilize this coefficient to carry out torture test combination road conditions adjustment and corresponding structural damage comparative analysis thereof, the method comprises following concrete steps:

The first step: alternating load the compiling load spectrum of testing vehicle structure under selected combination road conditions

(1) determine combination road conditions, select three kinds and the above lower strengthening road combination of pavement grade;

(2) structural loads test, carries out load test to the damage dangerous point of vehicle important structure;

(3) compiling load spectrum, application rain flow method carries out respectively counting statistics to vehicle structural loads under each single road conditions effect.

Second step: calculate the vehicle structure impairment value under each road conditions condition

Application glyphworks software programming Fatigue Damage Calculation flow process, according to the S-N characteristic of vehicle structure material, calculates the fatigue damage of vehicle structure under every kind of road conditions effect.

The 3rd step: according to damage equivalent principle, take a certain road conditions as benchmark, calculate the equivalent coefficient of vehicle structural damage under other road conditions conditions

(1) suppose that the fatigue damage producing equates (being Fatigue Damage Equivalence) with the damage producing under i kind road surface under j kind road surface, have the relation of formula (1) to set up,

$\frac{x_j}{y_j}=\frac{x_{\mathrm{ij}}}{y_i}$ Formula (1)

In formula, x _jrepresent j kind road surface mileage, x _ijrepresent equivalent mileage when i kind road surface is equal with respect to j kind pavement damage, y _jrepresent x _jthe fatigue damage amount that mileage effect produces, y _irepresent i kind road surface x _ithe fatigue damage amount that mileage effect produces;

(2) calculate that under arbitrary road conditions condition, vehicle structure fatigue damage is with respect to the equivalent mileage of fatigue damage under a certain concern road conditions condition, through type (1) calculates and tries to achieve:

$x_{\mathrm{ij}}=\frac{y_i{\·x}_j}{y_j}$ Formula (2)

From formula (2), x _iwith x _ijequivalent, i.e. x _ijto i kind road surface mileage x _iequivalent mileage;

(3) calculate under arbitrary road conditions condition vehicle structure fatigue damage with respect to the equivalent coefficient α of fatigue damage under a certain concern road conditions condition _ij, can further try to achieve equivalent coefficient α by formula (2) _ij, i.e. formula (3),

${\mathrm{\α}}_{\mathrm{ij}}=\frac{x_{\mathrm{ij}}}{x_i}$ Formula (3)

The 4th step: utilize equivalent coefficient, need to adjust combination road conditions according to user, and analyze corresponding vehicle structure damage

(1) according to Automobile Enterprises or user's needs, optional test mileage X _i(comprise road conditions kind j and weight proportion m thereof with test combinations road conditions condition _j);

(2) utilize the equivalent coefficient on each road surface of calculating in the 3rd step, determine all kinds of road conditions test miles X _j; X _jcalculate and try to achieve by formula (4),

$X_j=\frac{X_i\·m_j}{{\mathrm{\α}}_{\mathrm{ij}}}$ Formula (4)

(3) the total damage D under computational analysis target road conditions, can be by asking for the fatigue damage D of every kind of road conditions (j kind road conditions) _jtry to achieve, have formula (5)

D=ΣD _j

$D_j=\frac{y_i}{x_j}\·X_j$ Formula (5)

Thus, calculate the vehicle structure fatigue damage under ownership goal road conditions.

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